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            <h2 class="toc-title">目录</h2>
            <div class="toc-content" id="toc-content-auto"></div>
        </div><article class="page single"><h1 class="single-title animate__animated animate__flipInX">C语言之指针</h1><div class="post-meta">
            <div class="post-meta-line"><span class="post-author"><a href="/" title="Author" rel="author" class="author"><i class="fas fa-user-circle fa-fw" aria-hidden="true"></i>MC</a></span>&nbsp;<span class="post-category">收录于 <a href="/categories/c%E8%AF%AD%E8%A8%80/"><i class="far fa-folder fa-fw" aria-hidden="true"></i>C语言</a></span></div>
            <div class="post-meta-line"><i class="far fa-calendar-alt fa-fw" aria-hidden="true"></i>&nbsp;<time datetime="2017-11-14">2017-11-14</time>&nbsp;<i class="fas fa-pencil-alt fa-fw" aria-hidden="true"></i>&nbsp;约 4187 字&nbsp;
                <i class="far fa-clock fa-fw" aria-hidden="true"></i>&nbsp;预计阅读 9 分钟&nbsp;<span id="/c%E8%AF%AD%E8%A8%80%E4%B9%8B%E6%8C%87%E9%92%88/" class="leancloud_visitors" data-flag-title="C语言之指针">
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        </div><div class="details toc" id="toc-static"  data-kept="">
                <div class="details-summary toc-title">
                    <span>目录</span>
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                <div class="details-content toc-content" id="toc-content-static"><nav id="TableOfContents">
  <ul>
    <li><a href="#1-指针的简单使用">1. 指针的简单使用</a>
      <ul>
        <li><a href="#1-地址运算符">1. 地址运算符&amp;</a></li>
        <li><a href="#2指针简介">2.指针简介</a></li>
        <li><a href="#2-指针的简单使用">2. 指针的简单使用</a>
          <ul>
            <li><a href="#1-间接运算符">1. 间接运算符</a></li>
            <li><a href="#2-空指针和空类型的指针">2. 空指针和空类型的指针</a></li>
          </ul>
        </li>
      </ul>
    </li>
    <li><a href="#2-多重指针">2. 多重指针</a></li>
    <li><a href="#3-指针与数组">3. 指针与数组</a>
      <ul>
        <li><a href="#1--指针与一维数组">1.  指针与一维数组</a></li>
        <li><a href="#2-指针的危险性">2. 指针的危险性</a></li>
        <li><a href="#3-指针与二维数组">3. 指针与二维数组</a></li>
        <li><a href="#4-数组指针与指针数组">4. 数组指针与指针数组</a>
          <ul>
            <li><a href="#1-指针数组">1. 指针数组</a></li>
            <li><a href="#2-数组指针">2. 数组指针</a></li>
          </ul>
        </li>
      </ul>
    </li>
    <li><a href="#思考题">思考题</a></li>
    <li><a href="#结语">结语</a></li>
  </ul>
</nav></div>
            </div><div class="content" id="content"><h1 id="c语言之指针">C语言之指针</h1>
<p>在谈论指针之前，我们先看看地址。地址是指存储单元的编号。我们可以通过这个地址找到他所对应的存储单元，然后进行操作。（可以将地址理解为学生的学号，房间的房号。）可以说，地址指向某一变量的存储单元，所以，将地址形象话的称为“指针”。那么指针到底是什么呢？
从根本上来看指针是一个值为内存地址的变量（或者数据对象）</p>
<h2 id="1-指针的简单使用">1. 指针的简单使用</h2>
<h3 id="1-地址运算符">1. 地址运算符&amp;</h3>
<p>在计算机中每一个变量都存储在内存中，每一个变量都有其对应的地址空间，我们可以通过取地址符来得到它所对应的地址。这就是一元运算符“&amp;”的作用。假如有一个int型的变量a，我们可以通过<code>&amp;a</code>得到他的地址。
看如下程序：</p>
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<pre tabindex="0" class="chroma"><code><span class="lnt">1
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<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="cp">#include</span> <span class="cpf">&lt;stdio.h&gt;</span><span class="cp">
</span></span></span><span class="line"><span class="cl"><span class="cp"></span><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="n">a</span> <span class="o">=</span> <span class="mi">2</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="nf">printf</span><span class="p">(</span><span class="s">&#34;%d %p</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">,</span> <span class="n">a</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">);</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>上面的程序对于大家来说是既熟悉又陌生，这里来说明一下。
%p表示的是输出地址的说明符。
假设a的地址是0061FEAC（PC中地址通常使用16进制形式表示），那么上面的程序的输出结果是：
<code>2 0061FEAC</code>
总结：地址运算符&amp;是单目运算符，也称为一元运算符，&amp;运算符可以获取变量的地址。</p>
<h3 id="2指针简介">2.指针简介</h3>
<p>通过最开始的讲解我们已经了解了指针，也知道了指针是一个值为内存地址的变量。也就是说我们可以将通过&amp;运算符取出的地址赋给一个变量。</p>
<p>下面我们来讲解一下如何申请这样的变量。</p>
<p>声明指针变量时必须声明指针所指向的变量类型，因为不同的变量类型占用不同大小的存储空间。int和float可能占用相同大小的存储空间，但是他们所存储的数字去大不相同。所以我们可以使用指针变量所指向的变量类型 + “*” + 变量名来声明一个变量。
上面说了很多，可以理解起来不太容易，下面是一些指针变量声明的示例：</p>
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<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="kt">int</span> <span class="o">*</span> <span class="n">a</span><span class="p">;</span>		<span class="c1">// a是指向int类型变量的指针
</span></span></span><span class="line"><span class="cl"><span class="c1"></span><span class="kt">char</span> <span class="o">*</span> <span class="n">b</span><span class="p">;</span>		<span class="c1">// b是指向char类型变量的指针
</span></span></span><span class="line"><span class="cl"><span class="c1"></span><span class="kt">float</span> <span class="o">*</span> <span class="n">c</span><span class="p">;</span>		<span class="c1">// c是指向float类型变量的指针
</span></span></span></code></pre></td></tr></table>
</div>
</div><p>a 是指向int型变量的指针指的是a可以存储一个int型变量的地址。
还有个可能不理解的地方是指针变量。
相信大家有个疑惑，我们说，a是指向int型变量的指针，那么a到底是什么类型呢？a的值是一个地址，在大多数的系统中，地址是由一个无符号的整数表示的。但是不要把指针认为是整数类型。</p>
<h3 id="2-指针的简单使用">2. 指针的简单使用</h3>
<p>前面讲了好多，都是一些理论，现在来讲解一些简单的应用。</p>
<h4 id="1-间接运算符">1. 间接运算符</h4>
<p>现在可以声明一个指针变量，并且可以得到一个变量的地址进行赋值，如下：</p>
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<pre tabindex="0" class="chroma"><code><span class="lnt">1
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<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="kt">int</span> <span class="n">a</span> <span class="o">=</span> <span class="mi">2</span><span class="p">;</span>
</span></span><span class="line"><span class="cl"><span class="kt">int</span> <span class="o">*</span> <span class="n">b</span> <span class="o">=</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">;</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>指针b存储了a的地址，假设现在不知道b所储存的地址是哪个变量的，而想得到它的值，该怎么办呢？
现在就该间接运算符*登场了。间接运算符“*”，有时也称解引用符。作用是找到某个指针变量上的地址上的之值，然后对这个地址进行取值等操作，所以也被称为取值运算符。</p>
<ol>
<li>*的作用是取值，得到某个地址变量上的值。
看如下程序：</li>
</ol>
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<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="cp">#include</span> <span class="cpf">&lt;stdio.h&gt;</span><span class="cp">
</span></span></span><span class="line"><span class="cl"><span class="cp"></span><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="n">a</span> <span class="o">=</span> <span class="mi">2</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="o">*</span><span class="n">b</span> <span class="o">=</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="n">c</span> <span class="o">=</span> <span class="o">*</span><span class="n">b</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="nf">printf</span><span class="p">(</span><span class="s">&#34;c = %d</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">,</span> <span class="n">c</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">	<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><ol start="2">
<li>解引用符的作用不止于此，还可以通过解引用符改变指针变量所指的值。
看下面程序：</li>
</ol>
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</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="cp">#include</span> <span class="cpf">&lt;stdio.h&gt;</span><span class="cp">
</span></span></span><span class="line"><span class="cl"><span class="cp"></span><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="n">a</span> <span class="o">=</span> <span class="mi">2</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="o">*</span><span class="n">b</span> <span class="o">=</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="nf">printf</span><span class="p">(</span><span class="s">&#34;a = %d</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">,</span> <span class="n">a</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">	<span class="o">*</span><span class="n">b</span> <span class="o">=</span> <span class="mi">3</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="nf">printf</span><span class="p">(</span><span class="s">&#34;a = %d</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">,</span> <span class="n">a</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">	<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>a的值通过*b的赋值操作被改变了。上面的这种用法在函数中的引用比较多。</p>
<p>这儿我们来说明一下指针变量的类型的意义，通过解引用符可以取得指针变量所指向的值。众所周知，变量在内存中是存储的是二进制，那些指针变量的类型就告诉系统如何去获得这个值。指针变量的类型在读取这块所提供的信息是，指针变量所指向的值占空间的大小和“读”的方式。（就像前面提到过的int和float）</p>
<h4 id="2-空指针和空类型的指针">2. 空指针和空类型的指针</h4>
<p>C语言设置了一个指针常量“NULL”，空指针不指向任何存储单元。空指针可以赋给任何类型的指针变量。
C语言中有一种void类型，它的意思是空，在函数中，可以用来说明一个函数的返回值为空。在指针中可以说明一个指针可以指向任意的类型，当然，在指向具体的类型时，必须进行强制类型转化。</p>
<h2 id="2-多重指针">2. 多重指针</h2>
<p>之前说过，每一个变量都有其对应的地址空间，我们可以通过取地址符来得到它所对应的地址。那么也可以通过取地址符取得指针变量的地址。看如下程序：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt"> 1
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<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="cp">#include</span> <span class="cpf">&lt;stdio.h&gt;</span><span class="cp">
</span></span></span><span class="line"><span class="cl"><span class="cp"></span><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="n">a</span> <span class="o">=</span> <span class="mi">2</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="o">*</span> <span class="n">b</span> <span class="o">=</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="nf">printf</span><span class="p">(</span><span class="s">&#34;a的地址是：%p, 指针变量b的地址是：%p&#34;</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">b</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">	<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl"><span class="err">结果：</span>
</span></span><span class="line"><span class="cl"><span class="n">a</span><span class="err">的地址是：</span><span class="mf">0061F</span><span class="n">EAC</span><span class="p">,</span> <span class="err">指针变量</span><span class="n">b</span><span class="err">的地址是：</span><span class="mf">0061F</span><span class="n">EA8</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>a和b的关系入下图所示：
<img
        class="lazyload"
        src="/svg/loading.min.svg"
        data-src="https://img-blog.csdn.net/20171114200050166?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"
        data-srcset="https://img-blog.csdn.net/20171114200050166?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast, https://img-blog.csdn.net/20171114200050166?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast 1.5x, https://img-blog.csdn.net/20171114200050166?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast 2x"
        data-sizes="auto"
        alt="https://img-blog.csdn.net/20171114200050166?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"
        title="这里写图片描述" />
注：指针变量在32位系统中占4个字节，在64位系统（更准确的说是32位编译器和64位编译器，因为64位机器上可以运行32位的编译器）中占8个字节。指针变量所占内存的大小可以通过sizeof()函数计算。</p>
<p>既然也可以获得指针变量的值，那么该将这个值赋给谁呢？看下面的一行代码。
<code>int ** a;</code>
上面的这行代码说明a是指向int型指针变量的指针。它的作用是改变指针变量的值。看如下程序：</p>
<div class="highlight"><div class="chroma">
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<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="cp">#include</span> <span class="cpf">&lt;stdio.h&gt;</span><span class="cp">
</span></span></span><span class="line"><span class="cl"><span class="cp"></span><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="n">a</span> <span class="o">=</span> <span class="mi">2</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="n">b</span> <span class="o">=</span> <span class="mi">12</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="o">*</span> <span class="n">c</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="o">**</span> <span class="n">d</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="n">c</span> <span class="o">=</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="nf">printf</span><span class="p">(</span><span class="s">&#34;*c = %d</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">,</span> <span class="o">*</span><span class="n">c</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">	<span class="n">d</span> <span class="o">=</span> <span class="o">&amp;</span><span class="n">c</span><span class="p">;</span>	<span class="c1">// 将c的地址赋给d
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>	<span class="o">*</span><span class="n">d</span> <span class="o">=</span> <span class="o">&amp;</span><span class="n">b</span><span class="p">;</span> <span class="c1">// 通过*d改变c的值
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>	<span class="nf">printf</span><span class="p">(</span><span class="s">&#34;*c = %d</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">,</span> <span class="o">*</span><span class="n">c</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">	<span class="nf">printf</span><span class="p">(</span><span class="s">&#34;*d = %p, c = %p, &amp;b = %p</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">,</span> <span class="o">*</span><span class="n">d</span><span class="p">,</span> <span class="n">c</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">b</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">	<span class="nf">printf</span><span class="p">(</span><span class="s">&#34;**d = %d, *c = %d, b = %d</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">,</span> <span class="o">**</span><span class="n">d</span><span class="p">,</span> <span class="o">*</span><span class="n">c</span><span class="p">,</span> <span class="n">b</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">	<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl"><span class="err">结果：</span>
</span></span><span class="line"><span class="cl"><span class="o">*</span><span class="n">c</span> <span class="o">=</span> <span class="mi">2</span>
</span></span><span class="line"><span class="cl"><span class="o">*</span><span class="n">c</span> <span class="o">=</span> <span class="mi">12</span>
</span></span><span class="line"><span class="cl"><span class="o">*</span><span class="n">d</span> <span class="o">=</span> <span class="mf">0061F</span><span class="n">EA4</span><span class="p">,</span> <span class="n">c</span> <span class="o">=</span> <span class="mf">0061F</span><span class="n">EA4</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">b</span> <span class="o">=</span> <span class="mf">0061F</span><span class="n">EA4</span>
</span></span><span class="line"><span class="cl"><span class="o">**</span><span class="n">d</span> <span class="o">=</span> <span class="mi">12</span><span class="p">,</span> <span class="o">*</span><span class="n">c</span> <span class="o">=</span> <span class="mi">12</span><span class="p">,</span> <span class="n">b</span> <span class="o">=</span> <span class="mi">12</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>可以得到如下等式：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt">1
</span><span class="lnt">2
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="o">*</span><span class="n">d</span> <span class="o">==</span> <span class="n">c</span>
</span></span><span class="line"><span class="cl"><span class="o">**</span><span class="n">d</span> <span class="o">==</span> <span class="n">b</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>a是一个指向int型指针变量的指针，可以这样理解<code>int * (* a)</code>，&rsquo;* a&rsquo;说名a是一个指针，<code>int *</code>说明a所指向的是一个int型指针变量的指针。这种方式在函数中很常用。</p>
<h2 id="3-指针与数组">3. 指针与数组</h2>
<h3 id="1--指针与一维数组">1.  指针与一维数组</h3>
<p>数组在内存中占用的是一段连续的内存空间，并且数组名是数组首元素的地址。也就是说，如果a是一个数组，那么则会有<code>a == &amp;a[0]</code>。
a和&amp;a[0]都可以表示数组首元素的地址，我们可以将其赋给指针变量，然后可以通过这个指针进行操作，看如下程序：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt"> 1
</span><span class="lnt"> 2
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<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="cp">#include</span> <span class="cpf">&lt;stdio.h&gt;</span><span class="cp">
</span></span></span><span class="line"><span class="cl"><span class="cp"></span><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="n">a</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span> <span class="o">=</span> <span class="p">{</span><span class="mi">0</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">},</span> <span class="n">i</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="o">*</span> <span class="n">p</span> <span class="o">=</span> <span class="n">a</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">	<span class="k">if</span> <span class="p">(</span><span class="n">a</span> <span class="o">==</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">[</span><span class="mi">0</span><span class="p">])</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">		<span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="mi">5</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">			<span class="nf">printf</span><span class="p">(</span><span class="s">&#34;a[%d] = %d &amp;a[%d] = %p, p = %p *p = %d</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">,</span> <span class="n">i</span><span class="p">,</span> <span class="n">a</span><span class="p">[</span><span class="n">i</span><span class="p">],</span> <span class="n">i</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">[</span><span class="n">i</span><span class="p">],</span> <span class="n">p</span><span class="p">,</span><span class="o">*</span><span class="n">p</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">			<span class="n">p</span> <span class="o">=</span> <span class="n">p</span> <span class="o">+</span> <span class="mi">1</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">		<span class="p">}</span>
</span></span><span class="line"><span class="cl">	<span class="p">}</span>
</span></span><span class="line"><span class="cl">	<span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>上面的程序验证了数组名和数组首元素的地址相同。
大家可能感到奇怪的地方是p加一之后为什么会指向下一个数组元素。
在大多数系统中int类型的变量占4个字节。<strong>而指针加1指的是增加一个储存单元</strong>，对于上面的程序而言，p每增加1增加4个字节。并且因为数组在内存中占用的是一段连续的存储空间，所以上面的程序的一个结果如下所示：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt">1
</span><span class="lnt">2
</span><span class="lnt">3
</span><span class="lnt">4
</span><span class="lnt">5
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="n">a</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">=</span> <span class="mi">0</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">=</span> <span class="mf">0061F</span><span class="n">E94</span><span class="p">,</span> <span class="n">p</span> <span class="o">=</span> <span class="mf">0061F</span><span class="n">E94</span> <span class="o">*</span><span class="n">p</span> <span class="o">=</span> <span class="mi">0</span>
</span></span><span class="line"><span class="cl"><span class="n">a</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="o">=</span> <span class="mi">1</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="o">=</span> <span class="mf">0061F</span><span class="n">E98</span><span class="p">,</span> <span class="n">p</span> <span class="o">=</span> <span class="mf">0061F</span><span class="n">E98</span> <span class="o">*</span><span class="n">p</span> <span class="o">=</span> <span class="mi">1</span>
</span></span><span class="line"><span class="cl"><span class="n">a</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="o">=</span> <span class="mi">2</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span> <span class="o">=</span> <span class="mf">0061F</span><span class="n">E9C</span><span class="p">,</span> <span class="n">p</span> <span class="o">=</span> <span class="mf">0061F</span><span class="n">E9C</span> <span class="o">*</span><span class="n">p</span> <span class="o">=</span> <span class="mi">2</span>
</span></span><span class="line"><span class="cl"><span class="n">a</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span> <span class="o">=</span> <span class="mi">3</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span> <span class="o">=</span> <span class="mf">0061F</span><span class="n">EA0</span><span class="p">,</span> <span class="n">p</span> <span class="o">=</span> <span class="mf">0061F</span><span class="n">EA0</span> <span class="o">*</span><span class="n">p</span> <span class="o">=</span> <span class="mi">3</span>
</span></span><span class="line"><span class="cl"><span class="n">a</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span> <span class="o">=</span> <span class="mi">4</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span> <span class="o">=</span> <span class="mf">0061F</span><span class="n">EA4</span><span class="p">,</span> <span class="n">p</span> <span class="o">=</span> <span class="mf">0061F</span><span class="n">EA4</span> <span class="o">*</span><span class="n">p</span> <span class="o">=</span> <span class="mi">4</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>第一行中p = 0061FE94，在p+1之后的第二行中p = 0061FE98，刚好相差4。
<img
        class="lazyload"
        src="/svg/loading.min.svg"
        data-src="https://img-blog.csdn.net/20171114200206473?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"
        data-srcset="https://img-blog.csdn.net/20171114200206473?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast, https://img-blog.csdn.net/20171114200206473?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast 1.5x, https://img-blog.csdn.net/20171114200206473?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast 2x"
        data-sizes="auto"
        alt="https://img-blog.csdn.net/20171114200206473?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"
        title="这里写图片描述" /></p>
<h3 id="2-指针的危险性">2. 指针的危险性</h3>
<p>指针在C语言中非常重要，但是也同样非常危险。在C语言中如果一个变量没有被赋值，而去使用时，它会是一个随机的值，例如：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt">1
</span><span class="lnt">2
</span><span class="lnt">3
</span><span class="lnt">4
</span><span class="lnt">5
</span><span class="lnt">6
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="cp">#include</span> <span class="cpf">&lt;stdio.h&gt;</span><span class="cp">
</span></span></span><span class="line"><span class="cl"><span class="cp"></span><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">  <span class="kt">int</span> <span class="n">a</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">  <span class="nf">printf</span><span class="p">(</span><span class="s">&#34;%d</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">,</span> <span class="n">a</span><span class="p">);</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>每次运行的结果都会不一样。指针变量也不例外。那么如果直接使用这个变量时可能会发生一个无法预知的事情。</p>
<p>注：<font color=red>在全局变量中的系统会将一个没有初始化的变量初始化为0，指针变量初始化为NULL</font></p>
<p>在比如上面的p指针可以直接加5访问到数组之外的内存，如果将未分配的内存改变了，可能会对程序的运行产生一些影响。
下面来说一下下标运算符[]，对，你看的没错，就是数组的中使用的[]。下面的程序中可以看出下标运算符的实质。
看下面这段程序：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt"> 1
</span><span class="lnt"> 2
</span><span class="lnt"> 3
</span><span class="lnt"> 4
</span><span class="lnt"> 5
</span><span class="lnt"> 6
</span><span class="lnt"> 7
</span><span class="lnt"> 8
</span><span class="lnt"> 9
</span><span class="lnt">10
</span><span class="lnt">11
</span><span class="lnt">12
</span><span class="lnt">13
</span><span class="lnt">14
</span><span class="lnt">15
</span><span class="lnt">16
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="cp">#include</span> <span class="cpf">&lt;stdio.h&gt;</span><span class="cp">
</span></span></span><span class="line"><span class="cl"><span class="cp"></span><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">    <span class="kt">int</span> <span class="n">a</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span> <span class="o">=</span> <span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span> <span class="p">,</span><span class="mi">3</span> <span class="p">,</span><span class="mi">4</span><span class="p">},</span> <span class="n">i</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">    <span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="mi">4</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">        <span class="nf">printf</span><span class="p">(</span><span class="s">&#34;%d %d</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">,</span> <span class="n">a</span><span class="p">[</span><span class="n">i</span><span class="p">],</span> <span class="o">*</span><span class="p">(</span><span class="n">a</span> <span class="o">+</span> <span class="n">i</span><span class="p">));</span>
</span></span><span class="line"><span class="cl">    <span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="err">结果：</span>
</span></span><span class="line"><span class="cl"><span class="mi">1</span> <span class="mi">1</span>
</span></span><span class="line"><span class="cl"><span class="mi">2</span> <span class="mi">2</span>
</span></span><span class="line"><span class="cl"><span class="mi">3</span> <span class="mi">3</span>
</span></span><span class="line"><span class="cl"><span class="mi">4</span> <span class="mi">4</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>a的首地址相当于a数组第一个元素的地址，显然a[1]就相当于给a加上了1，然后取值。也就是：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt">1
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="o">*</span><span class="p">(</span><span class="n">a</span> <span class="o">+</span> <span class="mi">1</span><span class="p">)</span> <span class="o">==</span> <span class="n">a</span><span class="p">[</span><span class="mi">1</span><span class="p">];</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>下面和说一下指针与二维数组。</p>
<h3 id="3-指针与二维数组">3. 指针与二维数组</h3>
<p>其实没有真正的二维数组，二维数组在内存中也是存储在一段连续的存储空间中。
看如下程序。</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt"> 1
</span><span class="lnt"> 2
</span><span class="lnt"> 3
</span><span class="lnt"> 4
</span><span class="lnt"> 5
</span><span class="lnt"> 6
</span><span class="lnt"> 7
</span><span class="lnt"> 8
</span><span class="lnt"> 9
</span><span class="lnt">10
</span><span class="lnt">11
</span><span class="lnt">12
</span><span class="lnt">13
</span><span class="lnt">14
</span><span class="lnt">15
</span><span class="lnt">16
</span><span class="lnt">17
</span><span class="lnt">18
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="cp">#include</span> <span class="cpf">&lt;stdio.h&gt;</span><span class="cp">
</span></span></span><span class="line"><span class="cl"><span class="cp"></span><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">  <span class="kt">int</span> <span class="n">array</span><span class="p">[</span><span class="mi">3</span><span class="p">][</span><span class="mi">3</span><span class="p">]</span> <span class="o">=</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">    <span class="p">{</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">},</span>
</span></span><span class="line"><span class="cl">    <span class="p">{</span><span class="mi">4</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">6</span><span class="p">},</span>
</span></span><span class="line"><span class="cl">    <span class="p">{</span><span class="mi">7</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">9</span><span class="p">}</span>
</span></span><span class="line"><span class="cl">  <span class="p">};</span>
</span></span><span class="line"><span class="cl">  <span class="kt">int</span> <span class="n">i</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">  <span class="kt">int</span> <span class="o">*</span> <span class="n">ptr</span> <span class="o">=</span> <span class="o">&amp;</span><span class="n">array</span><span class="p">[</span><span class="mi">0</span><span class="p">][</span><span class="mi">0</span><span class="p">];</span>
</span></span><span class="line"><span class="cl">  <span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="mi">9</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">    <span class="nf">printf</span><span class="p">(</span><span class="s">&#34;%d &#34;</span><span class="p">,</span> <span class="o">*</span><span class="p">(</span><span class="n">ptr</span> <span class="o">+</span> <span class="n">i</span><span class="p">));</span>
</span></span><span class="line"><span class="cl">  <span class="p">}</span>
</span></span><span class="line"><span class="cl">  <span class="nf">printf</span><span class="p">(</span><span class="s">&#34;</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">  <span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl"><span class="err">结果：</span>
</span></span><span class="line"><span class="cl"><span class="mi">1</span> <span class="mi">2</span> <span class="mi">3</span> <span class="mi">4</span> <span class="mi">5</span> <span class="mi">6</span> <span class="mi">7</span> <span class="mi">8</span> <span class="mi">9</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>从上面的这段程序中可以看出二维数组正真的存储方式。
<img
        class="lazyload"
        src="/svg/loading.min.svg"
        data-src="https://img-blog.csdn.net/20171114200306622?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"
        data-srcset="https://img-blog.csdn.net/20171114200306622?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast, https://img-blog.csdn.net/20171114200306622?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast 1.5x, https://img-blog.csdn.net/20171114200306622?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast 2x"
        data-sizes="auto"
        alt="https://img-blog.csdn.net/20171114200306622?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvc3RhcmV4cGxvZGU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast"
        title="这里写图片描述" />
接下来的程序使用了指针代替下标运算符进行遍历二维数组，看下面的程序：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt"> 1
</span><span class="lnt"> 2
</span><span class="lnt"> 3
</span><span class="lnt"> 4
</span><span class="lnt"> 5
</span><span class="lnt"> 6
</span><span class="lnt"> 7
</span><span class="lnt"> 8
</span><span class="lnt"> 9
</span><span class="lnt">10
</span><span class="lnt">11
</span><span class="lnt">12
</span><span class="lnt">13
</span><span class="lnt">14
</span><span class="lnt">15
</span><span class="lnt">16
</span><span class="lnt">17
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="cp">#include</span> <span class="cpf">&lt;stdio.h&gt;</span><span class="cp">
</span></span></span><span class="line"><span class="cl"><span class="cp"></span><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">  <span class="kt">int</span> <span class="n">array</span><span class="p">[</span><span class="mi">3</span><span class="p">][</span><span class="mi">3</span><span class="p">]</span> <span class="o">=</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">    <span class="p">{</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">},</span>
</span></span><span class="line"><span class="cl">    <span class="p">{</span><span class="mi">4</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">6</span><span class="p">},</span>
</span></span><span class="line"><span class="cl">    <span class="p">{</span><span class="mi">7</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">9</span><span class="p">}</span>
</span></span><span class="line"><span class="cl">  <span class="p">};</span>
</span></span><span class="line"><span class="cl">  <span class="kt">int</span> <span class="n">i</span><span class="p">,</span> <span class="n">j</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">  <span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="mi">3</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">    <span class="k">for</span> <span class="p">(</span><span class="n">j</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">j</span> <span class="o">&lt;</span> <span class="mi">3</span><span class="p">;</span> <span class="n">j</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">      <span class="nf">printf</span><span class="p">(</span><span class="s">&#34;%d &#34;</span><span class="p">,</span> <span class="o">*</span><span class="p">(</span><span class="o">*</span><span class="p">(</span><span class="n">array</span> <span class="o">+</span> <span class="n">i</span><span class="p">)</span> <span class="o">+</span> <span class="n">j</span><span class="p">));</span>
</span></span><span class="line"><span class="cl">    <span class="p">}</span>
</span></span><span class="line"><span class="cl">    <span class="nf">printf</span><span class="p">(</span><span class="s">&#34;</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">  <span class="p">}</span>
</span></span><span class="line"><span class="cl">  <span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>从上面的的程序可以可出，指针和下标运算符之间的关系如下：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt">1
</span><span class="lnt">2
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="n">array</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="o">=</span> <span class="o">*</span><span class="p">(</span><span class="n">array</span> <span class="o">+</span> <span class="mi">1</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="n">array</span><span class="p">[</span><span class="mi">2</span><span class="p">][</span><span class="mi">1</span><span class="p">]</span> <span class="o">=</span> <span class="o">*</span><span class="p">(</span><span class="o">*</span><span class="p">(</span><span class="n">array</span> <span class="o">+</span> <span class="mi">2</span><span class="p">)</span> <span class="o">+</span> <span class="mi">1</span><span class="p">)</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>当然还可以将其推广至三维，四维&hellip;</p>
<h3 id="4-数组指针与指针数组">4. 数组指针与指针数组</h3>
<p>数组指针和指针数组是两个比较容易混淆的概念。下面先来简单解释下他们分别是什么意思。</p>
<ul>
<li>指针数组：指针数组是一个数组，其中所存储的变量是指针变量。也就是说，数组指针是由指针变量构成的数组。</li>
<li>数组指针：指针数组是一个指针，是指向一个数组的指针。</li>
</ul>
<h4 id="1-指针数组">1. 指针数组</h4>
<p>数组的元素可以是各种类型，当然也可以是指针类型，如果每个数组元素的类型都为指针，则称该数组为指针数组。换句话说，指针数组是由指针变量构成的数组。一维指针数组的定义形式如下：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt">1
</span><span class="lnt">2
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="err">类型名</span> <span class="o">*</span> <span class="err">数组名</span><span class="p">[</span><span class="err">数组长度</span><span class="p">];</span>
</span></span><span class="line"><span class="cl"><span class="err">例如：</span><span class="kt">int</span> <span class="o">*</span> <span class="n">a</span><span class="p">[</span><span class="mi">5</span><span class="p">];</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>为何是上面的这种定义呢？这是因为**[]的优先级比*高**，所以首先a是一个大小为5的数组，该数组中元素的类型为<code>int *</code>。
一个简单的小例子：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt"> 1
</span><span class="lnt"> 2
</span><span class="lnt"> 3
</span><span class="lnt"> 4
</span><span class="lnt"> 5
</span><span class="lnt"> 6
</span><span class="lnt"> 7
</span><span class="lnt"> 8
</span><span class="lnt"> 9
</span><span class="lnt">10
</span><span class="lnt">11
</span><span class="lnt">12
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="cp">#include</span> <span class="cpf">&lt;stdio.h&gt;</span><span class="cp">
</span></span></span><span class="line"><span class="cl"><span class="cp"></span><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">  <span class="kt">int</span> <span class="n">a</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span> <span class="o">=</span> <span class="p">{</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">5</span><span class="p">};</span>
</span></span><span class="line"><span class="cl">  <span class="kt">int</span> <span class="o">*</span> <span class="n">array</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span> <span class="o">=</span> <span class="p">{</span><span class="o">&amp;</span><span class="n">a</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">[</span><span class="mi">1</span><span class="p">],</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">[</span><span class="mi">2</span><span class="p">],</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">[</span><span class="mi">3</span><span class="p">],</span> <span class="o">&amp;</span><span class="n">a</span><span class="p">[</span><span class="mi">4</span><span class="p">]};</span>
</span></span><span class="line"><span class="cl">  <span class="kt">int</span> <span class="o">**</span> <span class="n">ptr</span> <span class="o">=</span> <span class="n">array</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">  <span class="kt">int</span> <span class="n">i</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">  <span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="mi">5</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">    <span class="nf">printf</span><span class="p">(</span><span class="s">&#34;%d &#34;</span><span class="p">,</span> <span class="o">**</span><span class="n">ptr</span><span class="p">);</span>  <span class="c1">// *p == &amp;a[i];
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>    <span class="n">ptr</span><span class="o">++</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">  <span class="p">}</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><h4 id="2-数组指针">2. 数组指针</h4>
<p>指针变量的类型可以是任何类型，当然也可以数组类型，一个指向数组的指针称为数组指针。它的定义形式如下：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt">1
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="err">类型名</span> <span class="p">(</span><span class="o">*</span> <span class="err">变量名</span><span class="p">)[</span><span class="err">数组长度</span><span class="p">];</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>下面的程序是一个小例子：</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt"> 1
</span><span class="lnt"> 2
</span><span class="lnt"> 3
</span><span class="lnt"> 4
</span><span class="lnt"> 5
</span><span class="lnt"> 6
</span><span class="lnt"> 7
</span><span class="lnt"> 8
</span><span class="lnt"> 9
</span><span class="lnt">10
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</span><span class="lnt">12
</span><span class="lnt">13
</span><span class="lnt">14
</span><span class="lnt">15
</span><span class="lnt">16
</span><span class="lnt">17
</span><span class="lnt">18
</span><span class="lnt">19
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="cp">#include</span> <span class="cpf">&lt;stdio.h&gt;</span><span class="cp">
</span></span></span><span class="line"><span class="cl"><span class="cp"></span><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">  <span class="kt">int</span> <span class="n">array</span><span class="p">[</span><span class="mi">3</span><span class="p">][</span><span class="mi">3</span><span class="p">]</span> <span class="o">=</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">    <span class="p">{</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">},</span>
</span></span><span class="line"><span class="cl">    <span class="p">{</span><span class="mi">4</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">6</span><span class="p">},</span>
</span></span><span class="line"><span class="cl">    <span class="p">{</span><span class="mi">7</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">9</span><span class="p">}</span>
</span></span><span class="line"><span class="cl">  <span class="p">};</span>
</span></span><span class="line"><span class="cl">  <span class="kt">int</span> <span class="n">i</span><span class="p">,</span> <span class="n">j</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">  <span class="kt">int</span> <span class="p">(</span><span class="o">*</span><span class="n">ptr</span><span class="p">)[</span><span class="mi">3</span><span class="p">]</span> <span class="o">=</span> <span class="n">array</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">  <span class="n">ptr</span> <span class="o">=</span> <span class="n">array</span><span class="p">;</span>
</span></span><span class="line"><span class="cl">  <span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="mi">3</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">    <span class="k">for</span> <span class="p">(</span><span class="n">j</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">j</span> <span class="o">&lt;</span> <span class="mi">3</span><span class="p">;</span> <span class="n">j</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">      <span class="nf">printf</span><span class="p">(</span><span class="s">&#34;%d &#34;</span><span class="p">,</span> <span class="o">*</span><span class="p">(</span><span class="o">*</span><span class="p">(</span><span class="n">ptr</span> <span class="o">+</span> <span class="n">i</span><span class="p">)</span> <span class="o">+</span> <span class="n">j</span><span class="p">));</span>
</span></span><span class="line"><span class="cl">    <span class="p">}</span>
</span></span><span class="line"><span class="cl">    <span class="nf">printf</span><span class="p">(</span><span class="s">&#34;</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">  <span class="p">}</span>
</span></span><span class="line"><span class="cl">  <span class="k">return</span> <span class="mi">0</span><span class="p">;</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>上面的这段程序对于初学的你来说是难以理解的，但是当你掌握这个的时候说明你已经初步的掌握指针了。
对于这句<code>int (*ptr)[3] = array;</code>，可以这样理解：
首先<code>* ptr</code>表明ptr是一个指针，然后接下来就是类型了。假设现在有一个<code>int a[3] = {1, 2, 3}</code>，其中a的类型是数组，那么可以这样认为a的类型是int[3]。那么指针ptr所指向的指针类型为int[3]。</p>
<h2 id="思考题">思考题</h2>
<p>想想输出为什么是那样？</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt"> 1
</span><span class="lnt"> 2
</span><span class="lnt"> 3
</span><span class="lnt"> 4
</span><span class="lnt"> 5
</span><span class="lnt"> 6
</span><span class="lnt"> 7
</span><span class="lnt"> 8
</span><span class="lnt"> 9
</span><span class="lnt">10
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-c" data-lang="c"><span class="line"><span class="cl"><span class="cp">#include</span> <span class="cpf">&lt;stdio.h&gt;</span><span class="cp">
</span></span></span><span class="line"><span class="cl"><span class="cp"></span><span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">{</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="n">a</span><span class="p">[</span><span class="mi">5</span><span class="p">];</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="o">*</span> <span class="n">ptr1</span> <span class="o">=</span> <span class="p">(</span><span class="kt">int</span> <span class="o">*</span><span class="p">)</span> <span class="p">(</span><span class="o">&amp;</span><span class="n">a</span> <span class="o">+</span> <span class="mi">1</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">	<span class="kt">int</span> <span class="o">*</span> <span class="n">ptr2</span> <span class="o">=</span> <span class="p">(</span><span class="kt">int</span> <span class="o">*</span><span class="p">)</span> <span class="p">((</span><span class="kt">int</span><span class="p">)</span><span class="n">a</span> <span class="o">+</span> <span class="mi">1</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">	<span class="nf">printf</span><span class="p">(</span><span class="s">&#34;%x %x</span><span class="se">\n</span><span class="s">&#34;</span><span class="p">,</span> <span class="n">ptr1</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">],</span> <span class="o">*</span><span class="n">ptr2</span><span class="p">);</span>
</span></span><span class="line"><span class="cl">	
</span></span><span class="line"><span class="cl">	<span class="k">return</span> <span class="mi">0</span><span class="p">;</span> 
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><h2 id="结语">结语</h2>
<p>关于指针这些肯定是不够的，指针是C语言中的难点，重点，需要平时多敲多练。</p>
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